Grazers superimpose humidity effect on stream biofilm resistance and resilience to dry-rewet stress.

Temperate low order streams increasingly experience intermittency and drying due to climate change. In comparison to well-studied Mediterranean streams, drying events in canopied temperate streams occur under higher ambient humidity which probably affects the metabolic response to drying. Previous work on drying sediments (in temperate streams) did not consider the interactions of trophic levels.

Environmental Control on Microbial Turnover of Leaf Carbon in Streams - Ecological Function of Phototrophic-Heterotrophic Interactions.

In aquatic ecosystems, light availability can significantly influence microbial turnover of terrestrial organic matter through associated metabolic interactions between phototrophic and heterotrophic communities. However, particularly in streams, microbial functions vary significantly with the structure of the streambed, that is the distribution and spatial arrangement of sediment grains in the streambed. It is therefore essential to elucidate how environmental factors synergistically define the microbial turnover of terrestrial organic matter in order to better understand the ecological role of photo-heterotrophic interactions in stream ecosystem processes.

Shading and sediment structure effects on stream metabolism resistance and resilience to infrequent droughts.

Perennial, temperate, low-order streams are predicted to become intermittent as a result of irregular droughts caused by global warming and increased water demand. We hypothesize that stream metabolism changes caused by irregular droughts are linked to the shading and bed sediment structure of temperate streams. We set up 16 outdoor experimental streams with low or high shade conditions and streambeds either with alternating sorted patches of gravel and sand or homogeneous gravel-sand mix sediment structures.

Fungal-bacterial dynamics and their contribution to terrigenous carbon turnover in relation to organic matter quality.

Ecological functions of fungal and bacterial decomposers vary with environmental conditions. However, the response of these decomposers to particulate organic matter (POM) quality, which varies widely in aquatic ecosystems, remains poorly understood. Here we investigated how POM pools of substrates of different qualities determine the relative contributions of aquatic fungi and bacteria to terrigenous carbon (C) turnover.

Phase-preserving parametric wavelength conversion to SWIR band in highly nonlinear dispersion stabilized fiber.

The first successful translation of a phase modulated optical signal over 80 THz, from the near infrared to the short-wave infrared (SWIR) band is demonstrated. A signal, phase-modulated at 10 Gbps, was received in an error-free manner in the SWIR(1.7-2.

Noise performance of phase-insensitive multicasting in multi-stage parametric mixers.

Noise properties of large-count spectral multicasting in a phase-insensitive parametric mixer were investigated. Scalable multicasting was achieved using two-tone continuous-wave seeded mixers capable of generating more than 20 frequency non-degenerate copies. The mixer was constructed using a multistage architecture to simultaneously manage high Figure-of-Merit frequency generation and suppress noise generation.

Continuous-wave four-wave mixing in cm-long Chalcogenide microstructured fiber.

We present the experimental demonstration of broadband four-wave mixing in a 2.5 cm-long segment of AsSe Chalcogenide microstructured fiber. The parametric mixing was driven by a continuous-wave pump compatible with data signal wavelength conversion.

Reconfigurable parametric channelized receiver for instantaneous spectral analysis.

We propose and demonstrate a photonic approach to a reconfigurable channelized radio frequency (RF) receiver for instantaneous RF spectrum monitoring and analysis. Our approach relies on the generation of high quality copies of the RF input by wavelength multicasting in a 2- pump self-seeded parametric mixer and the use of off-the-shelf filtering element such as Fabry-Perot etalon and wavelength division demultiplexers. The parametric channelizer scheme trades frequency non-degeneracy of the newly generated copies for ease of filtering design.

Performance trade-offs in single-photon avalanche diode miniaturization.

Single-photon avalanche diodes (SPADs) provide photons' time of arrival for various applications. In recent years, attempts have been made to miniaturize SPADs in order to facilitate large-array integration and in order to reduce the dead time of the device. We investigate the benefits and drawbacks of device miniaturization by characterizing a new fast SPAD in a commercial 0.

Low-frequency electrophoretic actuation of nanoscale optoentropic transduction mechanisms.

Inherent bistabilities within DNA-assembled fluorescent resonant energy transfer systems demonstrated time-varying optical signals in response to an electrophoretic driving force. Frequency responses of electrophoretically driven FRET systems were shown to be sequence specific. Integration of these signals over time gave near single-molecule sensitivity within a high background of autofluorescence.

Self-aligned spatial filtering using laser optical tweezers.

We present an optical spatial filtering device that has been integrated into a microfluidic system and whose motion and alignment is controlled using a laser optical tweezer. The lithographically patterned micro-optical spatial filter device filters out higher frequency additive noise components by automatically aligning itself in three dimensions to the focus of the laser beam. This self-alignment capability is achieved through the attachment of a refractive optical element directly over the circular aperture or pinhole of the spatial filter.

Laser-tweezer-controlled solid immersion microscopy in microfluidic systems.

We describe the creation and implementation of a near-field scanning solid immersion microscope that is specifically tailored for use in microfluidic systems. The microscope comprises a newly fabricated Weierstrass solid immersion lens (SIL), which is detached from its substrate and is free floating in the fluid, and a laser optical tweezer, which serves both as a trapping beam for alignment and positioning of the SIL and as a near-field scanning beam that images the sample through the SIL. A discussion of the SIL's fabrication method is presented along with experimental results that demonstrate the effectiveness of our microscope design.